The present invention relates to an improved crutch structure.
As shown in FIG. 1, a conventional crutch structure is mainly composed of an armpit seat 11, lateral tubes 12, handle 13, middle supporting tube 14, bottom cap 15 and telescopic tube 16. FIG. 3 shows the cross-section of the engaged supporting tube 14 and lateral tubes 12, wherein the supporting tube 14 has a central circular tube section 143 and two lateral outward projecting sections 142. Each projecting section 142 has a concave arch top surface suitable to snugly abut against and engage with the lateral tube 12 by means of rivets. As shown in FIG. 2, the supporting tube 14 is inserted into the bottom cap 15, while the lateral tubes 12 are not fitted thereinto and the lower ends of the lateral tubes 12 are plugged by end plugs 122. As shown in FIG. 5, a resilient fixing leaf member 161 is disposed inside a top end of the telescopic tube 16. The leaf member 161 has two free ends disposed with outward projecting bosses 1611 which extend through one of multiple pairs of fixing holes 141 formed on the supporting tube 14 so that the telescopic tube 16 can be adjustably telescopically fitted through the bottom cap 15 and inside the supporting tube 14. The outer diameter of the telescopic tube 16 matches with the diameter of a central through hole of the bottom cap 15, allowing the telescopic tube 16 to snugly and freely slide relative to the bottom cap 15. The inner diameter of the supporting tube 14 is slightly larger than the outer diameter of the telescopic tube 16 so as to avoid abrasion between the telescopic tube 16 and the supporting tube 14. In addition, referring to FIG. 4, the handle 13 has a shaft member 131 having two arch end surfaces suitable to snugly abut against the lateral tubes 12. The shaft member 131 is sleeved by a sponge sleeve 132 and formed with a central through hole, whereby the shaft member 131 can be clamped between the lateral tubes 12 and an elongated thread rod 133 can be extended through the central through hole of the shaft member 131 to secure with a butterfly nut 134 so as to lock the handle 13 on the lateral tubes 12.
Several shortcomings exist in the above conventional crutch structure as follows:
1. The lateral tubes 12 are engaged with the supporting tube 14 in such a manner that the lateral tubes 12 are first attached to the arch surfaces of the projecting sections 142 and then fixed thereon by means of rivets. Accordingly, in case a large force is exerted on the crutch in a normal direction for a period of time, the crutch is liable to deform and bend at the rivet position A as shown in FIG. 6. Therefore, the safety in use of the crutch cannot be insured.
2. In case the crutch is 45 degrees inclinedly placed relative to the ground and the armpit of a user is supported by the armpit seat 11, when a large force is suddenly exerted on the handle 13, the crutch is apt to deform and bend or even break at the fixing hole position S of the lateral tube 12 due to decreased strength, as shown in FIG. 7.
3. The supporting tube 14 is inserted into the bottom cap 15 while the lateral tubes 12 are not fitted thereinto and are plugged by the plug members 122. Therefore, the waste chips produced during processing or accumulated water D is unable to be exhausted from the lateral tubes 12. As a result, the inner walls of the lateral tubes 12 is liable to be corroded by the accumulated water and the quality and safety in use of the crutch cannot be insured, as shown in FIG. 2.
4. The inner diameter of the supporting tube 14 is slightly larger than the outer diameter of the telescopic tube 16 so that a clearance is formed therebetween and the telescopic tube 16 is unable to closely attach to the inner wall of the supporting tube 14. As a result, when using the crutch, an unstable slightly vibrating feeling Q will occur, as shown in FIG. 2.